Not applicable.
The present invention relates generally to a medical device, and more particularly, to a bite block for use with a tubular airway. The invention can be used to prevent a critically ill or anesthetized subject or patient from inadvertently biting, disrupting, restricting or obstructing the airway.
A patient receiving medication under general anesthesia typically requires an artificial tubular airway or conduit from the external environment, through the mouth and pharynx, to the tracheobronchial tree opening. Common artificial tubular airways are the cuffed endotracheal tube and the laryngeal mask airway (xe2x80x9cLMAxe2x80x9d). The LMA includes three major components, namely (1) a generally triangular mask having an opening defined by an inflatable cuff that, in use, surrounds the glottic opening, (2) an airway connector for connection to an external mechanical ventilator or anesthesia machine, and (3) an arcuate tubular airway conduit corresponding in shape, size and radius to a human pharynx and oral cavity connected at one end to the mask and at a second end to the airway connector. The LMA device can be sized and shaped to conform to pediatric, juvenile or adult anatomy and is commercially available in several sizes to match clinical needs. The airway connector end of the LMA is referred herein to as the proximal end, while the mask end is referred to as the distal end.
The LMA can be disposable or reusable. The reusable plastic (e.g., silicone plastic) device can be reprocessed by high temperature steam autoclaving. With multiple cycles the mechanical properties of the plastic can be altered. The plastic can become brittle and prone to fracture under stress such as biting and potential severe patient harm from airway loss.
With the mask opening oriented toward the glottic opening, the mask is advanced past the teeth or gums and into the oral cavity of an anesthetized patient until resistance is encountered, thereby placing the distal end of the LMA in the cone shaped upper esophageal sphincter and the body of the mask over the glottic opening. The cuff is inflated to seal the glottic opening off from the surrounding tissue and to form a sealed conduit from the patient airway to the external environment. In use, the tubular conduit traverses the oral cavity and the teeth or gums. Patients undergoing general anesthesia with an LMA in place do not typically receive muscle relaxants or paralytic agents.
For proper LMA function, the tubular conduit must remain patent to the external environment at all times during use. Any process that obstructs or disrupts the tubular conduit is life threatening, as the patient is unconscious, the airway reflexes are obtunded, and ventilation is not otherwise possible. The passage of oxygen to the patient is reduced or eliminated. One such process is the involuntary patient response of biting or bringing the upper and lower teeth together in response to painful surgical stimuli such as cutting open the skin.
U.S. Pat. No. 3,756,244 (Kinnear and Havstad) discloses an elongated arched conduit that can be inserted into the mouth to act as an airway. This device is inserted next to, but does not surround, the tubular conduit. The width of the airway is also less than the diameter of the tubular conduit, so the conduit can be partially obstructed during involuntary biting. Using this device, it can be difficult to place other tubes and catheters as the oral cavity is occupied by two devices placed side by side. Several tubes are often inserted into the oral cavity during anesthesia for additional monitoring or drainage of the stomach.
U.S. Pat. No. 4,425,911 (Luomanen and Luomanen) is a bite block having a central rectangular channel and a pair of open channels on either side of the central channel. The central channel is not indexed to the diameter of an airway tubular conduit. Accordingly, the cross sectional area required to place the bite block and reliably prevent LMA obstruction is not minimized. The rectangular central channel is not long enough to push the tongue forward to prevent airway obstruction after the airway conduit is removed.
U.S. Pat. No. 4,495,945 (Liegner) discloses a bite block through which tubing or other apparatus can be inserted into the oral cavity.
The foregoing problems are solved and a technical advance is achieved in a bite block for preventing obstruction of a tubular conduit of an airway. When properly utilized in the oral cavity of a patient, the bite block will prevent the patient from obstructing the tubular conduit by biting. The bite block is particularly applicable for use in conjunction with a laryngeal mask airway of the type described in U.S. Pat. Nos. 4,509,514 and 4,995,388.
The bite block of the present invention generally corresponds in cross-sectional profile to the shape of a human oral-pharyngeal cavity, which can be described by an arc of a circle of a defined radius. The bite block includes a U-shaped channel that corresponds in size and shape to the predetermined curved tubular portion of an appropriate sized tubular conduit. The U-shaped channel is of slightly greater diameter, width, and height than the predetermined diameter of the tubular conduit so that, in use, the U-shaped channel is in substantial apposition to the tubular conduit on three sides. The cross-sectional shape of the U-shaped channel is generally hemicircular, with a radius slightly exceeding the outer predetermined radius of the corresponding tubular conduit. Substantially parallel sides of the U-shaped channel extend from the maximal diameter of the hemicircle, and are longer than the outer predetermined radius of the corresponding tubular conduit.
The bite block is placed in a patient by opening the mouth and placing the bite block over the installed tubular conduit with minimal or no manipulation of the tongue or conduit. The bite block covers and surrounds the tubular conduit as it transits the teeth and oral-pharyngeal cavity, and has sufficient length to push the tongue forward.
A feature of the present invention is that the bite block is adapted in size and shape to fit into the human oral-pharyngeal cavity, thereby minimizing the cross-sectional area of the bite block in the patient airway.
Another feature of the present invention is that the bite block can fit snugly on a tubular conduit of predetermined size and shape.
Still another feature of the presented invention is that the bite block is sufficiently long at the distal end to push the tongue forward and thereby prevent the tongue from obstructing the patient""s airway when no tubular conduit is in place.
An advantage of the present invention is that the bite block can be placed over an installed tubular conduit and can be positioned with little or no manipulation of the conduit or the patient""s tongue.
Another advantage of the present invention is that the bite block can be placed or removed without disconnecting a pre-placed tubular conduit from an external device such as a mechanical ventilator or an anesthesia machine.
Yet another advantage of the present invention is that it can be injection molded of a thermoplastic material in a single-cavity mold, thereby reducing the cost and complexity of manufacture.
Other objects, features and advantages will become apparent from the detailed description and annotated drawing of the presently preferred embodiment.